How can I get the size of the Text Widget in flutter

Question

I\'ve painted a shape for the background of my content of Text.

I want the background autoscale the Text, even the softWrap being true.

Answer 1

from inspiring of the Günter Zöchbauer

List _calcLastLineEnd(String msg) {
  // self-defined constraint
  final constraints = BoxConstraints(
    maxWidth: 800.0, // maxwidth calculated
    minHeight: 30.0,
    minWidth: 80.0,
  );
  final richTextWidget =
      Text.rich(TextSpan(text: msg)).build(context) as RichText;
  final renderObject = richTextWidget.createRenderObject(context);
  renderObject.layout(constraints);
  final boxes = renderObject.getBoxesForSelection(TextSelection(
      baseOffset: 0, extentOffset: TextSpan(text: msg).toPlainText().length));
  bool needPadding = false, needNextline = false;
  if (boxes.length < 2 && boxes.last.right < 630) needPadding = true;
  if (boxes.length < 2 && boxes.last.right > 630) needNextline = true;
  if (boxes.length > 1 && boxes.last.right > 630) needNextline = true;
  return [needPadding, needNextline];
}